If there is a large list of options in a dropdown in a Custom Field, the user must manually scroll through dozens of options to find the correct option.
This seems like the user experience should be greatly enhanced. Check out something like Mint.com when you want to select a category for a transaction. As you type, only the options that match what has been typed remain.
Basically, a user should have the option to type and use the up and down keys instead of needing to mouse and scroll for every dropdown. This would greatly improve task data entry.